There has been widespread interest in both atomic (I) and molecular (I.sub.2) iodine lasers in the last few years. Photodissociation I lasers and optically pumped I.sub.2 lasers have been investigated and reported on in the literature. I.sub.2 lasers offer tunable output from approximately 544 to 1350 nm and have been operated in both a pulsed and continuous wave (CW) mode of operation. The iodine atom (.sup.2 P1/2) has good energy storage characteristics and there are large scale programs underway for investigating the scaling of a fusion laser employing iodine. Also, recently, a chemically pumped iodine laser has been demonstrated.
A small, low power, rapidly pulsed or CW I laser would be extremely useful as a diagnostic tool for probing the lasing medium in lasers like those mentioned above that are being developed. Such things as medium homogeneity and small signal gain/loss can be determined by directing the output beam from the small I laser through the lasing medium of the laser being investigated. The condition of the output beam prior to entry into and after passing through the lasing medium being investigated can be monitored and changes in the output beam interpreted to analyze the medium being investigated. The only pulsed lasers presently available for this type of diagnostic measurement are photodissociation lasers employing iodine compounds such as CF.sub.3 I as the lasing medium. The CF.sub.3 I or similar compound is photodissociated to produce atomic iodine by use of flashlamps. The use of flashlamps to dissociate CF.sub.3 I or C.sub.3 F.sub.7 I contained in a quartz tube is taught in U.S. Pat. No. 3,900,803 issued to William Thomas et al. Unfortunately the CF.sub.3 I or similar compound dissociated to form the atomic iodine lasing medium does not recombine with 100% efficiency to reform the original iodide compound. This quickly leads to a degradation of the laser's output and the lasing cavity must be cleaned out and new iodide compound added after only a few shots of the laser. The cleaning out and adding new iodide compound is often required after two or three shots. The number of shots between cleanings has been increased somewhat in some instances by utilizing a process of freezing out impurities in the lasing medium. However, these prior art lasers cannot operate as a sealed system and rapidly pulsed operation is difficult because of the requirement for cleanout and the addition of fresh iodide compound. CW operation is not possible.
The need for an atomic iodine laser capable of extended pulsed or CW operation was recognized and this need is met by the present invention. Accordingly, one of the principal objects of the present invention is to provide an atomic laser capable of rapid repetitive pulsed or continuous operation over a long period of time without maintenance or replenishment of the lasing medium.
Another object of the present invention is to provide an atomic laser that is optically pumped by a laser beam and delivers an output beam of coherent radiation whose wavelength is independent of the wavelength of the pumping laser beam.